1. Field of the Invention
The present invention relates to a repair of a pattern defect of a base that is obtained by a technique of screen printing, e.g., plasma display panels. More particularly, the invention relates to a repair of a pattern defect of a printed material layer, which is performed after forming a variety of material layers, such as a dielectric layer and an electrode layer, on a substrate by a technique of screen printing.
2. Description of the Background Art
Screen printing (which is also called thick film printing) is a printing method in which a screen plate is placed in close proximity to a base and a pasty printing material is transferred from a screen mesh of a desired pattern to the base. This printing method is employed in forming a pattern of an electrode wire layer, a dielectric layer, a barrier rib portion, a phosphor layer or the like, on a substrate constituting a plasma display panel (PDP). Alternatively, this method is employed in forming a phosphor layer of a CRT (cathode ray tube), an electrode layer, a dielectric layer or the like of a printer head substrate.
In screen printing, after a printing material paste is transferred onto a substrate, a firing or heating process is performed under conditions suitable for the printing material paste to evaporate unneeded ingredients in the paste, thereby forming an electrode wire layer, a dielectric layer and the like on the substrate.
Such a screen printing is favorable for reducing manufacturing cost because of its low device cost and running cost. However, its pattern transfer accuracy is not so high and it is susceptible to a pattern defect Various improvements have been achieved to improve the transfer accuracy. However, for example, when a pattern of an electrode wire of a PDP is formed on a substrate (i.e., a base 35) by printing as shown in FIG. 7, defects might occur at several points in the overall electrode wire of the substrate. For the panel of a display device, such as a PDP, a printed pattern defect directly deteriorates the display quality of the display device. Therefore, if a printed defect occurs, it is necessary to repair the defect.
In conventional repair of printed pattern defects, a pattern defect is found by observation with a microscope or the naked eye, and then a repair material paste 37 having the same composition as the printing material of a material layer is printed to a defect position by using a repair screen 36 as a screen plate for repair, as shown in FIG. 8. A repair pattern 38 having a width identical to the pattern width of a material layer repaired, as shown in FIG. 9, has been formed in the repair screen 36. A repair printing is performed by squeezing the repair material paste 37 from the repair pattern 38 to a defective portion by using a squeegee 39. Thereafter, in order to fire the repair material paste 37 of the defective portion, the substrate is put into a firing furnace as shown in FIG. 10, having a construction similar to that in firing printed patterns, and then subjected to a re-firing for the entire surface of the substrate.
The conventional pattern defect repairs by means of printing, however, have difficulties in alignment between the repair screen 36 and a pattern defect. Specifically, a screen printing causes a mismatch of patterns between a screen pattern and a pattern of paste that has actually been printed on a base. Therefore, such a mismatch must be taken into consideration when making an alignment between a screen plate and a pattern defect. Also, a pattern to be printed may actually vary with the kind of screen pattern and printing paste used and situations where a printing is performed. Thus, the pattern defect repair by printing requires much time to adjust an alignment, resulting in a poor working efficiency.
In addition, since a repair screen 36 on which a material paste for repair has been put is placed on a substrate, the surface of the substrate might become dirty.
Moreover, due to the characteristics of screen printing, it is difficult to transfer a material paste for repair into a local defective portion so as to have a uniform thickness, and a variation is liable to occur. Further, a repaired portion tends to upheave, which might adversely affect the smoothness and the like of other material layers that are formed thereon after repair.
According to a first aspect of the present invention, a defect repair sheet of a printed pattern used in repairing a pattern defect of a material layer that is printed on a base by employing a screen plate includes a transparent sheet; a material layer for repair formed on the transparent sheet; and an adhesive layer formed on the transparent sheet so as to cover the material layer for repair, having an adhesive property to the base which makes it possible to transfer the material layer for repair to the base.
According to a second aspect, the defect repair sheet of the first aspect is characterized in that the material layer for repair is formed on the transparent sheet so as to have a predetermined pattern
According to a third aspect, the defect repair sheet of the first aspect is characterized in that the adhesive layer includes a layer composed of a material that evaporates during a firing processing, which is performed after transferring the material layer for repair and the adhesive laver to a defective portion of the base.
According to a fourth aspect, the defect repair sheet of the third aspect is characterized in that the material layer for repair includes a layer composed of an electrode material.
According to a fifth aspect, a defect repair device for repairing a pattern defect of a material layer that is printed on a base by using a screen plate employs a defect repair sheet in which a material layer for repair having a predetermined pattern is formed on a transparent sheet, and includes an alignment means for aligning a pattern of the material layer for repair of the defect repair sheet and a pattern defective portion of the material layer of the base; and a transfer means for transferring the material layer for repair to the defective portion by pressing the defect repair sheet on the base from a side on which the material layer for repair is not formed, along a formed pattern of the material layer for repair.
According to a sixth aspect, the defect repair device of the fifth aspect is characterized in that the defect repair sheet further includes comprises an adhesive layer formed on the transparent sheet so as to cover the material layer for repair, having an adhesive property to the base which makes it possible to transfer the material layer for repair to the base.
According to a seventh aspect, the defect repair device of the sixth aspect is characterized in that the adhesive layer includes a layer composed of a material that evaporates during a firing processing, which is performed after transferring the material layer for repair and the adhesive layer to a defective portion of the base.
According to an eighth aspect, the defect repair device of the fifth aspect is characterized in that the alignment means includes an image taking means that takes an image of the base to obtain an image data of a pattern of the material layer; image processing means that detects a contour of a pattern of the material layer based on the image data and detects whether the pattern has a defect to output a result of image processing; and a position adjusting means that, when a defect is present in the pattern of the material layer, adjusts a position of the base so that the defective portion has a certain positional relation with respect to the material layer for repair of the defect repair sheet previously positioned in a predetermined position.
According to a ninth aspect, the defect repair device of the eight aspect is characterized in that the image taking means takes, before obtaining the image data, an image of the defect repair sheet from a side on which the material layer for repair is not formed, to obtain a preliminary image data of the predetermined pattern of the material layer for repair that can be seen through the transparent sheet; the image processing means further detects a contour of the predetermined pattern based on the preliminary image data to output a result of a preliminary image processing; and the position adjusting means adjusts, before adjusting a position of the base, a position of the defect repair sheet so that a contour of the predetermined pattern matches the predetermined position, based on the result of preliminary image processing
According to a tenth aspect, the defect repair device of the ninth aspect is characterized in that the material layer includes a layer composed of an electrode material.
According to an eleventh aspect, a method for repairing a pattern defect of a material layer that is printed on a base by using a screen plate employs a defect repair sheet in which a material layer for repair having a predetermined pattern is formed on a transparent sheet, and includes the step of pressing the material layer for repair to a defective portion of a pattern of a material layer formed on the base to transfer the material layer for repair to the defective portion; and applying an irradiating laser to the material layer for repair transferred to the defective portion to fire the material layer for repair.
According to a twelfth aspect, the method of the eleventh aspect is characterized in that the defect repair sheet further includes an adhesive layer formed on the transparent sheet so as to cover the material layer for repair, having an adhesive property to the base which makes it possible to transfer the material layer for repair to the base.
According to a thirteenth aspect, the method of the twelfth aspect is characterized in that the adhesive layer includes a layer composed of a material that evaporates in a firing processing which is performed after transferring the material layer for repair and the adhesive layer to a defective portion of the base.
According to a fourteenth aspect, the method of the thirteenth aspect is characterized in that the material layer includes a layer composed of an electrode material.
In a first aspect according to the present invention, a defect repair sheet of a printed pattern used in repairing a pattern defect of a material layer formed by printing includes a transparent sheet, a material layer for repair formed on the transparent sheet, and an adhesive layer that is formed on the transparent sheet so as as to cover the material layer for repair and also has an adhesive property to a base. By pressing the material layer for repair of the defect repair sheet on a defective portion of a pattern, it is possible to easily and precisely transfer the material layer for repair to the defective portion by the function of the adhesive layer.
In a defect repair sheet according to a second aspect, a material layer for repair having a predetermined pattern is formed on a transparent sheet. This facilitates to determining the position of the material layer for repair that can be seen through the transparent sheet, based on image data and like, permitting the automation of defect repair.
In a defect repair sheet according to a third aspect, an adhesive layer includes a layer composed of a material whose ingredients evaporate when the adhesive layer is transferred to a base together with a material layer for repair and the material layer for repair is then fired. This prevents the unneeded adhesive layer from remaining on a base after firing.
In a defect repair device according to a fourth aspect, by using a defect repair sheet in which a material layer for repair having a predetermined pattern is formed on a transparent sheet, the material layer for repair and a pattern defective portion of a base are aligned by an alignment means, and then the material layer for repair is pressed and transferred on the defective portion by transfer means. This facilitates the automation of defect repair, improving the efficiency of defect repair.
In a method for repairing a printed pattern defect according to a fifth aspect, use of laser irradiation in firing a material layer for repair transferred to a defective portion permits making a brief firing for defect repair. In addition, the area occupied by an irradiation device for the irradiating laser is considerably smaller than that of a firing furnace, making it easy to ensure its space.
Accordingly, it is an object of the present invention to realize a simple and precise transfer of a repair material to a pattern defective portion and thus improve the working efficiency of the defect repair.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.